The usefulness of a monomer can be projected when the structure's reactive sites suggest an adaptation in certain fields of uses. For example, in the solid propellant field which requires polymers for binders, crosslinking sites are essential for developing propellant integrity and properties. Also, wherever a monomer is used to form structural materials from polymerization, the orientation of the backbone structure and location of unsaturated sites are significant. One such monomer, 2,3-diphenyl-1,3-butadiene, has been projected as an excellent monomer for making head-to-head polystyrene complete with vinyl unsaturation in polymer backbone. Thus, the described structure allows graft additions to be made which results, generally, in a large number of crosslinked polymer types of potential interest as structural materials.
The monomer 2,3-diphenyl-1,3-butadiene, has been synthesized from slow distillation of 2,3-diphenyl-2,3-dihydroxybutane from anhydrous KHSO.sub.4 and 2,3-diphenyl-butane-diol as disclosed by Justus Liebig's Annalen der Chemie, Band 570, page 212.
A related process for producing 2,3-diphenyl-1,3-butadiene is disclosed in Organic Syntheses - Vol. 50 by Issei Iwai et al. This disclosure relates to a process wherein the reaction product of anhydrous dimethyl sulfoxide and sodium hydride is reacted with diphenylacetylene in anhydrous dimethyl sulfoxide to produce a low yield (22-25%) of slightly impure 2,3-diphenyl-1,3-butadiene which after recrystallization from methanol gave about 10.7-13.6% of pure 2,3-diphenyl-1,3-butadiene.
The monomer, 2,3-diphenyl-1,3-butadiene, has also been prepared by reaction of 2,3-diphenyl-2,3-dihydroxybutane with acetyl bromide as disclosed by Canadian Journal of Research, Volume 17, Sec. B, page 80.
The first disclosed process has literature reported yields of about 80% of the monomer; however, multiple investigations in carrying out the disclosed process has revealed that great care is required in handling the reaction, and that verification of results reported were not achieved, both in the amount of yield and the monomer produced.
The second disclosed process does not yield a high enough yield of the desired monomer for its commercial acceptance as a starting monomer.
The third disclosed process by the Canadian Journal of Research results in a yield of 20.3%; however, a further improvement in processing to a higher yield of the monomer is desired to render its acceptance as a starting monomer for widespread use.
The monomer, 2,3-diphenyl-1,3-butadiene because of its potential usefulness as a result of the described modifications which can be readily achieved, would have enhanced value as a starting material if it could be made in high yield by a simple process of synthesis.
Therefore, an object of this invention is to provide a facile, high yield synthesis process for producing the monomer, 2,3-diphenyl-1,3-butadiene.
A further object of this invention is to provide a facile, four step process for synthesis of 2,3-diphenyl-1,3-butadiene starting with a compound which can be reacted to produce intermediates for further modification and conversion to the desired monomer.
Still a further object of this invention is to provide a facile, four step process for sythesis of 2,3-diphenyl-1,3-butadiene starting with the dimerization of acetophenone to produce the compound acetophenone pinacol which can be reacted to produce intermediates for further modification and conversion to the desired monomer.